Biograph mCT PET•CT Evaluation of Chemotherapy Response in Lymphoma

Detection of metabolic change following chemotherapy or chemoradiation.

Case 1: IntroductionFludeoxyglucose F 18* (18F FDG) PET and PET•CT are established as the mainstay of staging and restaging of lymphoma. 18F FDG PET is also very sensitive for detection of metabolic change in a tumor following chemotherapy or chemoradiation. The speed of response of a tumor to a particular therapy is of critical importance in response assessment and therapy continuation decisions.The more rapidly a tumor shrinks or faster the drop in tumor metabolic activity occurs, the more likely the response will be long standing. This is most obvious in therapy of lymphoma where residual masses are common following therapy completion in spite of significant and often complete remission of the disease as evident on 18F FDG PET•CT. Tumor masses in lymphoma are slow to decrease in size, often due to associated fibrosis and necrosis, although viable tumor burden may be grossly reduced. PET•CT following 1 or 2 cycles of chemotherapy is a reliable indicator of the metabolic response of the tumor to therapy and indicates the likelihood of a sustained remission.

*Siemens' PETNET Solutions is a manufacturer of fludeoxyglucose F 18 injection (18F FDG). Indication and important safety information as approved by the US Food and Drug Administration can be found at the bottom of the page for 18F FDG, adult dose 5-10 mCi, administered by intravenous injection.

A 24-year-old male presented with a mediastinal mass detected in chest radiography along with night sweats, weight loss and cough (B symptoms). The biopsy of mediastinal mass revealed diffuse large-cell B cell lymphoma (DLBCL). Clinically, the diagnosis was "bulky" DLBCL stage IIb. The patient was referred for 18F FDG PET•CT for initial staging. Initial staging PET•CT demonstrated an extensive hypermetabolic mediastinal nodal mass along with solitary involved nodes in both axilla, as well as deposits in the inner margin on the anterior thoracic wall in the anterior pleural recess. Fused PET•CT images show significant infiltration of the chest wall. High resolution and lesion contrast on the Biograph™ mCT delineates small axillary nodal involvement. The patient was put on an R-CHOP14 chemotherapy regime (Cyclophosphamide, Doxorubicin, Vincristine and Prednisolone) along with the monoclonal antibody rituximab given in cycles with 14-day intervals. Standard regime included 6 to 8 individual cycles. After 3 cycles, the patient underwent a follow-up 18F FDG PET•CT.

Case 2: IntroductionA second case demonstrates the difference between metabolic responses compared to change in tumor volume in lymphoma secondary to chemotherapy visualized on a Biograph mCT with high volumetric resolution and accurate SUV quantification.

Sequential PET•CT studies show significant decrease in tumor metabolism after 2 and 6 cycles of chemotherapy. The metabolic response after 2 cycles appears far higher compared to change in tumor size on CT.

History

A 14-year-old girl with a pelvic mass diagnosed as non-Hodgkin’s lymphoma by biopsy underwent initial staging with 18F FDG PET•CT in June 2011. The initial study showed a large hypermetabolic pelvic mass with 2 small peritoneal and 1 inguinal nodal lesions. The variegated appearance within the large tumor mass is typical of matted lymph nodes. The patient was given chemotherapy with an R-CHOP14 regime, and the first follow-up 18F FDG PET•CT scan was performed in August 2011, after 2 cycles of chemotherapy. Chemotherapy was continued for 4 more cycles and the patient again underwent PET•CT in January 2012, after the completion of 6 cycles of chemotherapy.

Sequential PET images show a considerable decrease in metabolic activity in the pelvic mass in the first scan performed after 2 cycles. There was, however, significant residual uptake in the pelvic lesion, as well as in the inguinal and peritoneal lesions. The second follow-up scan shows complete resolution of tumor uptake, and visually appears free of all hypermetabolic lesions. Sequential axial PET•CT fused slices at the level of the pelvis shows a hypermetabolic matted lymph nodal mass, which shows significant decrease in SUVmax and SUVpeak in the initial follow-up study with further decrease to normal levels after 6 cycles. The percentage decrease in maximum tumor diameter after 2 cycles (41%) was lower than that of SUVmax (57%) or SUVpeak (65%). The difference in response levels between SUVmax and SUVpeak, calculated using syngo®.via, also was striking and is illustrative of the fact that SUVpeak based on a 1cm³ volume around the highest activity voxel combined with a Biograph PET•CT with accurate quantification technology is a more robust statistical tool for the evaluation of therapy response.

These clinical examples illustrate the value of early 18F FDG PET•CT imaging in prediction of therapy response and long term prognosis in lymphoma.

*Fludeoxyglucose F 18 Injection

INDICATIONS AND USAGEFludeoxyglucose F 18 injection (18F FDG) is indicated for positron emission tomography (PET) imaging in the following setting:Oncology: For assessment of abnormal glucose metabolism to assist in the evaluation of malignancy in patients with known or suspected abnormalities found by other testing modalities, or in patients with an existing diagnosis of cancer.

IMPORTANT SAFETY INFORMATIONRadiation RisksRadiation-emitting products, including fludeoxyglucose F 18 injection, may increase the risk for cancer, especially in pediatric patients. Use the smallest dose necessary for imaging and ensure safe handling to protect the patient and health care worker.

Blood Glucose AbnormalitiesIn the oncology and neurology setting, suboptimal imaging may occur in patients with inadequately regulated blood glucose levels. In these patients, consider medical therapy and laboratory testing to assure at least two days of normoglycemia prior to fludeoxyglucose F18 injection administration.

Adverse ReactionsHypersensitivity reactions with pruritus, edema and rash have been reported; have emergency resuscitation equipment and personnel immediately available.

The statements by Siemens customers described herein are based on results that were achieved in the customer's unique setting. Since there is no "typical" hospital and many variables exist (e.g., hospital size, case mix, level of IT adoption) there can be no guarantee that other customers will achieve the same results.

*Fludeoxyglucose F 18 Injection Related Safety Information

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